Very hard in your hand, even harder when you try to hit them. Tennis elbow is in your future if you use them for any prolonged amount of time (aside from them shooting out of a ball machine). I agree with you zerojoshua about the Dunlop Grand Prix & Tretorns are even harder.

I don't think they are that much harder than 'regular' balls. I bought 108 of them in 2010 when I bought my ball machine and used them exclusively in it for two years hitting for probably at least 1 hour per week. I never had any arm or elbow problems from that. They are somewhat harder than pressured balls but they aren't like hitting rocks as some people are implying. The only reason I don't use them is that the outer felt finally wore off and they're pretty expensive to replace. I created a system to repressurize regular balls and now use it to keep my ball machine supplied with good balls.

I had a bucket of them with my ball machine, and I found them slightly firmer than regular tennis balls, but I would not describe them as "rocks" by any means. They hit pretty much like new firm balls.

For the tennis ball machine, I like these because they throw consistently vs balls with varying levels of compression.

And, I think I've felt more elbow pain when I've hit dead balls than I've felt from the Tretorns.

Warmed up with some new Micro X balls today ... my partner and I agreed they played like they were slightly heavier than a regular ball, but nothing that bothered us. We were hitting with new Penn ATP's at the same time for comparison. The Micro X's might have bounced slightly higher off the hard court (or maybe the ball has greater spin potential) but the difference was subtle.

From a static weight viewpoint, all these balls weigh the same. Out of the can, the Tretorns varied from 2.00 oz to 2.05 oz. The Penn ATP's varied from 2.00 oz to 2.10 oz.

I think that any player perceptions that the Tretorn's are slightly "heavier" or "harder" has to do with differences in the elasticity of the ball and differences in how they deform on impact. Would be interesting to watch a high-speed video to see if there are any visual differences.

My elbow can be a bit sensitive so only time will tell whether the bag I'm about to order will mess with my arm after some machine sessions.

The "hard" responses in this thread reaffirm my observation that many people here -- mostly the barely post pubescent -- speak of what they do not know. You have to be out of your M'fing mind to describe these as "hard as a rock". Or more likely, you have never used Micro-X balls, or have zero experience with other "pressureless type" balls. Typical TT.

The "hard" responses in this thread reaffirm my observation that many people here -- mostly the barely post pubescent -- speak of what they do not know. You have to be out of your M'fing mind to describe these as "hard as a rock". Or more likely, you have never used Micro-X balls, or have zero experience with other "pressureless type" balls. Typical TT.

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You could be right there. I have used a lot of preasureless balls over the years and the biggest complaint I have is the felt seems to wear off faster and you and up with really light balls. I have not really gone the Tretorn route yet as they are sooooo expensive. I did test some maybe 10 years ago but it was around the same time as we were testing the oversize rally ball and I dont remember much about the tretorns.

Still...if they last a long time they would be worth it in the long run. My concern is the felt going like it does on preasurless balls. I dont even mind if the balls are a little heavy. If they dont bounce in the cold forget it. We play in the rain and snow around here.

The "hard" responses in this thread reaffirm my observation that many people here -- mostly the barely post pubescent -- speak of what they do not know. You have to be out of your M'fing mind to describe these as "hard as a rock". Or more likely, you have never used Micro-X balls, or have zero experience with other "pressureless type" balls. Typical TT.

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I completely agree that the Micro-X are not "rock-hard". However, they are definitely harder compared to normal pressurized balls.

Gotta be clear here, are we comparing the Micro-X to other pressureless or normal balls.

I have always used the Micro-X with my Lobster until recently I switched to these Wilson Trainer pressureless balls. They are much cheaper at approx USD65 for a bag of 60. They don't lose their bounce and they are softer than the Micro-X.

IMO, these Wilson Trainer balls are the closest thing to a normal pressurized ball. However, I'm not sure if these Wilson Trainer is available in the States.

I couldn't find the Wilson "Trainer" ball at any of Wilson's international websites. Japan's version does show bags of a "00" pressureless practice ball. Also, some European tennis shops as well as TW Europe are selling a Wilson "Team" trainer ball for 85 Euros. With shipping to the US, that would be pricier than Micro-X from any US retailer.

I did a search on "pressureless balls" in this forum and there seem to be enough satisfied users of the Micro-X so I ordered a bag.

That said, I noticed Tretron has a "Micro-X Comfort" ball which Tretorn's website says is suited to cold climates or high-altitude play. I couldn't find any US vendors of bags however.

Yes this is the case. I used to use them. It takes some adjustment but after a couple of weeks it's doable. Gamma sells/sold pressureless balls directly as well; dig up one of their old catalogues and give them a call.

Strange, I played with mine outside just before Christmas. It was cold (39 degrees F). All other balls (some regular, some pressureless from other companies) -- were all dead. I threw out a bagful that day. The tretorns were the only ones which bounced. They did not feel heavy. If anything, they were a little "too bouncy" -- that's the only complaint.

Anyway, I have not found anything better yet.

The other presureless balls just lose their bounce overtime. I prefer to deal with extra liveliness of Tretorns. It is almost like opening a new can in the middle of the day in the summer.

I'm one of those that started using a ball machine with a set of Tretorn micro-x balls. I concur with the other folks here: they felt like hitting rocks! I quickly developed tennis elbow and switched back to regular balls . The micro-x definitely felt harder than any regular balls I had used. I can't compare to other pressureless brands, though.

To avoid spending a fortune on regular balls, I re-pressurize my existing balls with a couple of PressureBall tubes. They do work well, and they are a LOT cheaper than the commercial re-pressurizing kegs. There are a few other threads on PressureBall in this forum.

The "hard" responses in this thread reaffirm my observation that many people here -- mostly the barely post pubescent -- speak of what they do not know. You have to be out of your M'fing mind to describe these as "hard as a rock". Or more likely, you have never used Micro-X balls, or have zero experience with other "pressureless type" balls. Typical TT.